PROJECT ABSTRACT Diabetic Macular Edema (DME) is the leading cause of blindness in the working age population. The anti- VEGF agents Ranibizumab and Aflibercept are currently the standard of care for DME. However, these treatments are far from optimal: ~40% of the DME patients have an inadequate response to the treatment. Mover, patients have to receive regular intravitreal injections indefinitely, creating significant treatment burden. Two more anti-VEGF agents have since been tested in phase 3 trials; although they moderately increased drug duration (from 1-2 months to 3 months), both failed to further improve vision gain. Thus, relying on anti- VEGF agents alone is clearly insufficient to improve efficacy. Combination therapies, which combine an anti-VEGF agent with disease modifying agents that target other important biomarkers such as Ang2 and VEGF-C/D, have shown great promise in further improving efficacy and/or reducing treatment burden. However, they often require the use of multiple therapeutic agents and sometimes multiple injections, which further increase the cost and treatment burden. In order to address this shortcoming, the ideal next-generation DME treatment should meet the following criteria: a) small in size, in order to achieve high molar dosage and longer duration of efficacy, and facilitate tissue penetration; b) devoid of immunogenicity and immune-stimulatory effects, in order to ensure long-term safety; c) most importantly, capable of inhibiting multiple biomarkers with one molecule, in order to improve efficacy without increasing treatment burden and cost. Aptamers are single stranded oligonucleotides that bind to molecular targets in a manner similar to monoclonal antibodies (mAbs). Although aptamers were invented much more recently than mAbs, they have already shown significant potential as ocular therapeutics: Macugen, the first anti-VEGF agent approved by FDA for wet AMD treatment, is an aptamer; two more aptamers (Fovista and Zimura) have been tested in human trials for multiple retinal indications, making aptamers one of the most evaluated modality for retinal diseases, with a favorable safety profile and a clear regulatory pathway. The purpose of this SBIR is to develop highly stable, multi-specific aptamers that may serve as the optimal combination treatment for DME. To that end, the Aptitude team has accumulated extensive experience in aptamer discovery. We have previously developed the Particle Display method that significantly improves the aptamer performance. We have also developed the method to screen for the optimal linker for a bispecific aptamer. Moreover, we have made further improvement to directly screen for fully modified aptamers that may enable longer duration of efficacy. Our expertise in aptamer discovery is complemented by our collaborators? expertise in DME preclinical research and clinical trials. If successful, this project has the potential of bringing more efficacious and affordable treatment to DME patients.